Spherical And Its Optimal Design Of Conformal Array Beamforming Techniques

Array antennas consists of many radiators(elements), which conform to surface of the vehicles in order to reduce or eliminate the impact of aerodynamic performance, this antenna is known as conformal antennas. Conformal antennas with a low profile, light weight, easy to install on the aircraft surface, etc. Today,as the antenna technology developing continuouslly, more and more conformal antennas used in many other fields. Spherical array is to refer to all the array elements distributed in a sphere surface. As a kind of conformal array, spherical array owes all virtuals of the conformal array naturally. However, the unique shape makes it possess different radiation characteristics compare to usual array antenn. Planar arrays have the fundamental limitation on the maximum possible scan angle. If elements in the planar array are placed much closer than half of a wavelength, the mutual coupling will increase and therefore the array performance will be degraded. If they are placed further apart, the maximum scan angle is limited by grating lobes. For spherical array an active sector can be moved along surface. Thus, the scan angle is increased and the grating lobe phenomenon is reduced.This paper starts from a spherical antenna model, and gradually introduced the sparse, shaped-beam,and microstrip antenna elements application in the model. Genetic algorithms(GA) ,a global optimization method, is used in the analysis processing. Low-sidelobe array pattern synthesis techniques developed for linear and planer arrays do not work well with spherical arrays. In the synthesis of the spherical conformal antenna array, without regard to element pattern function, ignore the mutual coupling effects between array elements. Sparse the array exited with equal amplitude and cophase, maintaining the same array aperture, making the element positions as parameter, maximum relative sidelobe level as the optimization objective, reducing the number of array elements and system cost. In the antenna shaped-beam section, introduced narrow beam nulling and wide beam nulling. For each of the nulling, three analytical methods amplitude, phase and complex nulling is adopted to be simulation, analysis and comparison. In the process of genetic manipulation, encoding method is improved, fitness function is constructed not only considering nulling depth, but also the side lobe gain to maintain a certain level. Through the analysis of the antenna array pattern function, it is clear that in the interference direction, there is certain nulling depth, which suggests that radiation characteristc of the interference direction is confined effectively. Microstrip antenna with a light weight, low cost, easy installation features, maks it one of the most popular antenna types. So it has potential for a broad range of applications, especially in the conformal microstrip array, advantages of the array is better reflected. The paper replace all orient elements with microstrip array elements, observing and analyzing microstrip elements application in the spherical conformal array.